Circuits and apparatus for telephone-switchboards.



No. 741,713. PATENTED 001.20, 1903,.

. l s.,1s. PRBNTIss. Y

GIRGUITSAND AlPARATUs FOR TELEPHONE SWITGHBOARDS.

APPLIOATION FILED MAY 18,r 1901 N0 MODEL.

1lllllll l l Tn: uonms vivies co. uovo-uma. wumurou. n. c,

rte. 741,713.

UNITED STATESA 'Patented october 2o, 1905i.y

PATENT OFFICE.

CiRCUlTS AND APPARATUS FOR TELEPHONE-SWITCHBOARDS;

SPECIFICATION forming part vof Letters Patent Nol 741,713, dated october2o, 1903,

. Application filed May 18, 1901l .To all whom it may concern.-

Be it knownthat, SPENCER B. PRENTIss, at citizen of the United States,residing at Washington, in the District of Columbia, have in-` vented anew and useful Im rovement in Circuits and Apparatus forelephone-Switch-i boards, of which the following is a specification.

My invention relates to improvements inl circuits and apparatus fortelephone-switchboards, and more particularly to that portion thereof bymeans of which electrical connection may be eected between the variouslineterminals upon the board.

According to the practice now generally followed it is customary toprovide connectingplugs adapted to engage a spring or springsconstituting a so-called spi-img zf-jack,v in which a subscribers lineor a trunk-line terminates. These plugs are usually arranged in pairs,which are connected by flexible conductors, and in the circuit thusformed are usually arranged two `switches or keys, one to enable theoperator to connect her telephone into the circuit and the other toenable her to connect in a generator for the purpose of signaling asubscriber into whose line-jack one of the plugs has been inserted. Thepairs of plugs are arranged along the front of the switchboard, andthere should bea sufficient number of them to serve the jacks upon thesection of the board where they are located at the busiest time of theday. For this reason it is necessary to place the pairs very closetogether, and the switches orkeys above referred to are usually placedjust in front of the plugs with which they are designed to cooperate.These switches or keys, hereinafter termed, respectively, the listeningand the ringing keys, necessitate a multiplicity of spring-contacts, bymeans of which p the various circuit changes may be effected, and intheir cramped position it is difficult to make the necessary wireconnections with the springs, these connections when made forming acrowded mass of wires and soldered joints which are easily deranged andwhen out of order are diicult to repair; In the case of the ringing-keycontactsmust be provided whereby the generator-current may be A sent iueither direction, and at the same time the circuit in the oppositedirection is opened,

Serial No. 60,899. (No model.)

' necessitating the multiplication of contactsprings, while in the caseof the listening-key less or fewer contacts are necessary.

One of the objects of my invention is to greatly relieve this congestionof wiring and multiplicity of contacts by providing means which enableme to dispense with the usual ringing-keys and their appurtenances uponthe front of the board.

A further object is to diminish the number 0f movements of the operatorin making a connection, and thereby increase the efficiency of eachoperator.

A further object is to greatly simplify the wiring of the switchboardand to so arrange the ringing-keys that they will be easily accessiblefor purposes of repair without interfering with or injuring adjacentconnections, thereby reducing the original cost of installation and thecost of maintenance.

A furtherjobject is to provide a simple,

durable, and efficient connecting-plug for telephone-switchboards whichshall, besides serving its usual purposes, perform the functions of aringing-key.

With theseA objects in View the invention consists in providing aconnecting-circuit for electrical signaling-lines comprising a pair ofconductors and a third conductor and a source of signaling-currentconnected to the third conductor and to one conductorof the au'. l pf Itconsists, further, in providing a connecting-plug for electricalswitchboards having a tip and a sleeve contact, spring-contacts movablymounted upon the plug and adapted to engage alternately one of saidcontacts, and a suitable inclosing shell for the parts.

It consists, further, in the novel arrangement of circuits of atelephone-switchboard and the construction and arrangement of parts of atelephone-switchboard connectingplug hereinafter to be fully describedand claimed.

My invention is illustrated in the accompanying drawings, in which likereference characters indicate corresponding parts, and in which Figure lis a diagrammatic representation of a portion of a telephone-switchboardto which my invention is applied, two subscribers line-jacks and thestations to which they ICO are connected being shown and the Varioussignals being entirely omitted from the board. Fig. 2 is an enlargeddetail View, in central sectional elevation, of a preferred form ofconnecting-plug embodying the essential features of my invention. Fig. 3is a detail.

Referring to the drawings, X and Y are two subscribers stationsconnected by line-wires l 2 and 3 4, respectively, with jacks J and J'upon the switchboard at central office, each jack consisting of theusual spring and ring contacts j' 12. The usual instruments and circuitconnections at the subscribers sta tions are shown in diagram,comprising at station X a transmitter T, battery B, induction-coil l,receiver R, hook-lever H, generator g, and ringer Z7. Similarly atstation Y are shown transmitter T', battery B', induction-coil I',receiver R', hook-lever H', generator g', and ringer Z2'. At subscribersstation X, hereinafterdesignated the calling subscriber, the receiverRis shown removed from the hook and the lever H as in its raisedposition under the influence of its spring (not shown) to cut out thegenerator and ringer and close thelocal transmitter-circuit and also toconnect the receiver and the secondaryof theinducti'on-coil to line. Atstation Y, hereinafter designated the called subscriber, the receiver isshown upon t-he hook and the lever H' down to connect the ringer toline.l

In Fig. l a pair of connecting-plugs P P' are shown with their outercasings removed and inserted into line-jacks J J', respectively, theseplugs being connected by the usual cord-circuit conductors 5 6, theseconductors making connection between the sleeves and the tips of theplugs in a manner to be hereinat'ter more fully described. Thecentralofiice operators telephone, set is shown in diagram at O, theinduction-coil, switch-hook, and contacts being omitted and thetransmitter being shown on a closed circuit for the sake of clearness.This set is arranged to be bridged across the cord-circuit by means ofthe listeningkey L, consisting of springs ZZ', contacts Z2 t, plungerZ4, and operating-lever Z5, pivoted at l, all of Well-- knownconstruction. This portion of the circuits and apparatus being old andforming no part of the present invention may be varied in constructionat pleasure Without departing from the invention.

The calling or generator circuit and the means for connecting the samewith the lines which constitute the present invention will now beexplained in brief. One form of plug suitable for making the connectionswill then be described in detail and the operation of the circuits andapparatus as a whole will then be described.

An additional conductor 7 is added to the cord connecting the plugs Pand P', and at any suitable point a generator G is bridged across thisconductor and one of the voicecurrent conductors, as 6. The plugs are ofspecial construction, being provided with movable contacts by means ofwhich the voicecurrent circuit may be broken and the generator-circuitconnected to line. The contacts for making these circuit changes areshifted by subjecting the plugs to added pressure after they have beeninserted into the line-jacks, as will bev more fully explainedpresently. Normally the parts of the plug are in the position shown atP, Fig. l, and in Fig. 2 as a whole, in which the conductor 5 isconnected to spring s', `the latter being in contact with sleeve 192 ofthe plufr. Conductor 6 is in permanent connection with the tip 19' ofthe plug. The third or generator conductor 7 is connected to spring s2,the free end of which is normally out of contact with the sleeve 192.Both the springs s' and s2 are so mounted that, the plug beinginsertedinto the jack, when extra pressure is applied the parts take theposition shown at P', Fig. lthat is, spring s' is forced out ofengagement with sleeve 1)?, thus interrupting the talkingcircuit, andspring S2 engages said sleeve, completing the generator-circuit-Referring now more particularly to Fig. 2, A represents the shell orcasing of the plug inclosing the working parts. 19' is the tiprod, ofbrass, bronze, or other suitable metal, forming the base of the strncture, upon which is secured in any suitable manner the sleeve 192, also ofmetal, the two being separated by a tube of insulation z'. The sleeve192 is provided With a flange 193 at its inner end, against which abutsthe block of insulating material t". Slidingly mounted upon the tip-rodis a metallic sleeve 1?", having at its rear end a flange 1f. Thissleeve may be split a portion of its length from the end opposite theflange,

Aas shown in Fig. 3, in order to make a better contact with the rcd, thespring portions taking up the wear. The sleeve 19" carries a secondsleeve or boss 112, of insulting material, to which it is firmlysecured, and upon this second sleeve are mounted the contact-springs s's2, to which are secured the circuit-wires 5 and '7. Therearwardly-projecting portion of the sleeve t? is provided with achamber or recess to admit the nut 11G, the latter being adapted toengage external threads upon the rod 19' and limit the rearward movementof the sleeve 19I and sleeve t2. Between the insulating-block t' and thesleeve i2 is fitted a coiled spring S, which may be secured at one endto the tip-rod19' and at the other to the sleeve 1)', thus to make moreperfect electrical connection between these parts and maintain thesleevespand f2in theirextreme rearward position. The contact-springs s's2, mounted in any suitable manner upon the insulating-sleeve t2,project toward the forward end of the plug, the former, being normallyin contact and making electrical connection with the flange 193 of theplugfsleeve192. This spring s' is provided With a bend or projection sm,extending inwardly in such a manner as to be normally free of, butadapted to ride upon, the block t" IOO IIO

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when the sleeve t2 is forced Vforward against the action of the springS, therebyto take the lthrust of the spring s and lift its contact endout of engagement with the flange p3. The spring 32 is similarlymounted, preferably, on the opposite side of the sleeve 2, this springbeing shorter than spring s and normally supported by a bend orprojection S20, which rests upon block c", its free end being adapted tomake contact with flange p3 when sufficient pressure is applied to` theplug. A block or flange 3, preferably of insulating material, is rigidlysecured to the plug by any suitable means, such as a pin, (not shown,')with which block the plug-casing makes a sliding contact and closure.The rear end of the casing is provided with a central aperture to admitthe circuit-wires 5, 6, and '7, which pass therethrough and are secured,respectively, to springs s', terminal piece p7, which is in contact withsleeve p4, and spring s2, the rear end of the casing resting against andbeing secured to the sleeved? y The operation ofthe device and circuitsthus described is as follows: Supposing that the subscriber at station Xwishes to communicate with another subscriber, as Y, he signals centralin any suitable or well-known manner. Thereupon the .operator at centralinserts an answering-plug P into the jack J, forming the terminal ofthat line. The spring S of the plug is of such strength that it will notyield to the ordinary pressure necessary to force the plug into thejack-seat, so that the contact-springs s s2 of the plug P remain in thenormal position-that shown-whereby the calling-subscribers line isconnected with conductors 5 5. The operator then manipulates thelistening-key L in the usual manner and having ascertained the numberwanted Vreleases said key and inserts the calling-plug P in the jack J',(or into thejack of atrunkline leading to the section of the board uponwhich the jack of the wanted subscriber is located,) bringing sufficientadditional pressure to bear upon the plug to 'overcome the resilience ofspring S and move contactspring s out of engagement with lange p3 andspring s2 into contact therewith, thereby breaking the electricalconnection of conductor 5 with said flange and connecting conductor 7therewith. Current from the generator G (said generator being operatedby power or bythe free hand of the operator) now flows out to the calledstation over the following circuit: from generator G by wire 7 to springs2 of plug P, flangeps and sleevep2 to ring'j2 of jack J', line-wire 3to ringer h' and lever H' at station Y, wire 4, jack-sprlngj', plug-tipp', and return to generator by wire 6. Having thus given the call, theoperator re leases the plug-handle, when the parts immediately resumetheir normal position under action of spring S, as shown in plugP and inFig. 2. If the called subscriberfails to answer, the operator repeatsthe call. When the called subscriber answers, shouldl the calling sub-'scriber have left his phone all that is necessary to' recall him is forthe operator to press his plug to its extreme inward position to connectthe generator, thereby ringing back. It will thus be seen that byconstructing both plugs of each pair similarly I am enabled to dispensewith the two ringing-keys now usually employed, mounted upon the frontof the switchboard, together with their attendant complications ofcircuit connections and conother from a supply kept on hand for the pur?pose, and send it to the factory for repairs. The annoyance so wellknown to manufacturers of having to send an expert out to a switchboardwhich they have installed to overhaul the circuits is thus avoided inall cases where the trouble is inthe ringing device.

Although I have described specifically one form of plug embodying myinvention jas hav? ing the contact-springs engage the sleeve-contact ofthe plug, this is by no means essential, as these springs may bearranged diiferently, and many other changes in details of constructionand arrangement of parts may be made without departing from the spiritof the invention, and these I wish it to be un- Y stood fall strictlywithinthe scope and purview of the same.

Having described my invention, what I claim as new, and'desire to secureby Letters Patent of the United States, ilsl. Connecting means forterminals of electrical signaling-lines comprising a pair of conductorsVand a third conductor, a source of signaling-current permanentlyconnected to the third conductor and to one conductor of the pair, andswitching mechanism at the ends of said conductors cooperating withterminal contacts carried by said switching mechanism, substantially asdescribed.

2. In an electrical switchboard,lineterminals suitably placed thereon,connecting means comprising a pair of conductors and a third conductor,a source of sign aling-current permanently connected to the thirdconductor and to one conductor of the pair, and switching mechanism atthe ends of said conductors cooperating with terminal contacts forconnection with said line-terminals, substantially as described.

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connected to the third conductor and to one conductor of the pair, andswitching mechanism at the ends of said conductors coperating withterminal contacts carried by said switching mechanism for connectionwith said line-terminals, substantially as described.

4. In an` electrical switchboard, lineterminals suitably placed thereon,means for connecting said line-terminals comprising a pair of conductorsand a third conductor, a source of signaling-current permanentlyconnected to the third conductor and to one conductor of the pair,terminal contacts for connection with said line terminals, and switchingmechanism at the ends of said conductors cooperating with said terminalcontacts for connecting alternately (a) said pair of conductors, and(ZJ) one conductor of the pair and said third conductor, to aline-terminal, substantially as described.

5. In a telephone-switchboard, spring-jacks forming line terminalssuitably mounted thereon, a connecting-circuit comprising a pair ofconductors and a third conductor, a source of signaling-currentconnected to the third conductor and to one conductor of the pair, plugscarrying terminals for engagement with said spring-jacks, said plugsbeing provided With contacts movable relatively to said plug-terminalsand so arranged as to be adapted to connect to line alternately (a) saidpairofconductors, and (b) one of said pair and the third conductor,substantially as described.

6. A connecting-plug for telephone-switchboards comprising a tip and asleeve contact, spring-contacts movably mounted upon the plug andadapted to engage alternately one of said contacts, and a suitableinclosing shell for the parts, substantially as described.

7. A connecting-plug for telephone-switchboards comprising a tip and asleeve contact,

movable springs slidingly mounted thereon and adapted to engage one ofsaid contacts, means for making continuous electrical connection withthe other of said contacts, and means for maintaining the parts normallyin one position, substantially as described.

8. A connecting-plug for telephone-switchboards comprising a central rodforming the tip-contact, a sleeve-contact insulated therefrom, aconducting-sleeve slidingly mounted upon said rod and carrying a blockof insulation, contact-springs secured to said block of insulation andextending into proximity to the sleeve-contact, a spring adapted mmaintain normally the block of insulation in such a position that one ofsaid contactsprings will be in engagement with the sleevecontact, theparts being so arranged that when pressure is applied to the casing thelast-named contact-spring Will be moved out of engagement with thesleeve-contact and the remaining spring-contact Will be moved intoengagement therewith, substantially as described.

9. A connecting-plug for telephone-switchboards comprising a tip and asleeve contact, springs slidingly mounted thereon and adapted to engageone of said contacts, one of said springs having a bend or shoulder toengage a portion of the plug structure and having a contact portion toengage one of said plugcontacts, means for maintaining the partsnormally in one position, and suitable electrical connections,substantially as described.

10. A connecting plug for telephoneswitchboards comprising a tip and asleeve contact, springs slidingly mounted thereon and adapted to engageone of said contacts, a sleeve or block adjacent said contact to beengaged and through which current cannot pass to said contact, a bend orshoulder upon one of said springs to engage said sleeve or block, meansfor making continuous electrical connection with one of said contacts,and means for maintaining the parts normally in one position,substantially as described.

In testimony Whereoic I have signed my name to this specification in thepresence of two subscribing Witnesses.

SPENCER B. PRETISS,

Witnesses:

T. BLAIR SHOEMAKER, EMORY H. BOGLEY.

